Adds some more fixes and tweaks in the World Renderer class.

* Fixes that "pendingChunks" was never reset to false and thus caused the chunksInProximity list to be recreated each frame
* Removes the no longer necessary chunk mesh disposal while adding chunks to the render queues
* Adds that chunk meshes get removed from the VRAM via dispose() when leaving the chunksInProximity list
* Renamed some enums for consistency